On Mon, Oct 28, 2024 at 11:04:23AM +0530, Nikunj A Dadhania wrote:
> The hypervisor should not be intercepting RDTSC/RDTSCP when Secure TSC is
> enabled. A #VC exception will be generated if the RDTSC/RDTSCP instructions
> are being intercepted. If this should occur and Secure TSC is enabled,
> guest execution should be terminated as the guest cannot rely on the TSC
> value provided by the hypervisor.
This should be in the comment below.
> Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
> Tested-by: Peter Gonda <pgonda@xxxxxxxxxx>
> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> arch/x86/coco/sev/shared.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/coco/sev/shared.c b/arch/x86/coco/sev/shared.c
> index 71de53194089..c2a9e2ada659 100644
> --- a/arch/x86/coco/sev/shared.c
> +++ b/arch/x86/coco/sev/shared.c
> @@ -1140,6 +1140,16 @@ static enum es_result vc_handle_rdtsc(struct ghcb *ghcb,
> bool rdtscp = (exit_code == SVM_EXIT_RDTSCP);
> enum es_result ret;
>
> + /*
> + * RDTSC and RDTSCP should not be intercepted when Secure TSC is
> + * enabled. Terminate the SNP guest when the interception is enabled.
> + * This file is included from kernel/sev.c and boot/compressed/sev.c,
> + * use sev_status here as cc_platform_has() is not available when
> + * compiling boot/compressed/sev.c.
> + */
> + if (sev_status & MSR_AMD64_SNP_SECURE_TSC)
> + return ES_VMM_ERROR;
> +
> ret = sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, 0, 0);
> if (ret != ES_OK)
> return ret;
> --
> 2.34.1
>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
